30 Nature of the Formative Stimulus 



the zoospores which move about by means of their 

 vibratile flagella and into which these mononuclear 

 amoebae become transformed. And it is certain that 

 phenomena likewise nervous in character must come into 

 play when the cells of Magosphera planula become 

 separated from one another and each one moves off 

 independently by means of its cilia. 



One is justified then in suspecting that when these 

 cells are united in a colony they may then also be the 

 seat of phenomena of a nervous nature, and that the 

 other ontogenetic stages of these minute organisms ought 

 also to be attributed to such phenomena. 



But then we should have to refer the development of 

 higher organisms also to phenomena of the same nature. 



As a support of this hypothesis we recall the well 

 known fact that all cells of organisms, from these most 

 primitive pluricellular forms up, are united to one another 

 by a network of intercellular protoplasmic bridges. 



We recall the example which the different species of 

 Volvox afford, a genus of lower algae consisting of a 

 vesicle formed of a single layer of cells, very much like 

 the blastula stage of the development of animals. All 

 the species of Volvox show a perfectly typical and 

 regular form of union between the different cells of the 

 body. In Volvox aureus for example, the superficial 

 cells of the trophic hemisphere of the vesicle lie in a thick 

 soft gelatinous mucus and each is not only provided with 

 two long flagellae, but also is connected with each of 

 the five or six adjoining cells by a long, thin protoplasmic 

 filament. In the germinal hemisphere the protoplasmic 

 filaments are more numerous so that each of the great 

 spores which arise there is connected with each one of 

 the large neighboring cells by bundles of from three to 



